The present invention relates to an electrophotographic photosensitive member, particularly one having a photosensitive layer comprising a specific resin, a process cartridge and an electrophotographic apparatus including the electrophotographic photosensitive member, and a process for producing the electrophotographic photosensitive member.
Hitherto, as photoconductor materials for use in electrophotographic photosensitive members, inorganic materials, such as selenium, cadmium sulfide and zinc oxide, have been known. On the other hand, organic photoconductor materials, such as polyvinylcarbazole, phthalocyanine and azo pigments, are noted for their advantages, such as high productivity and non-pollution characteristic and have been widely used while they tend to be inferior in photoconductor performances and durability compared with inorganic materials.
In many cases, there have been used function separation-type electrophotographic photosensitive members having a structure including a charge generation layer and a charge transport layer in lamination so as to satisfy both electrical and mechanical characteristics. On the other hand, an electrophotographic photosensitive member is required to satisfy sensitivity, electrical characteristic, optical characteristic and durability corresponding to an electrophotographic process where it is used, as a matter of course.
Particularly, the surface of a photosensitive member is directly subjected to various electrical and mechanical external forces during various steps of charging, exposure, development with a toner, transfer onto paper and cleaning, so that durability against these forces is required. More specifically, the photosensitive member is required to exhibit durability against abrasion and occurrence of scars at the surface due to abrasion and also durability against surface abrasion due to charging.
The surface layer of the electrophotographic photosensitive member using an organic photoconductor is a thin resin layr, and the property of the resin is very important. As resins satisfying the above-mentioned requirements to some extent, acrylic resin, polycarbonate resin, etc., have been used commercially in recent years. However, this does not mean that all the above-mentioned properties are satisfied by these resins. Particularly, it is difficult to say that these resins have a sufficiently high film hardness in order to realize a higher durability. More specifically, a surface layer of these resins has been liable to cause abrasion or scars during repetitive use.
Further, in compliance with a demand for a higher sensitivity in recent years, relatively large amounts of low-molecular weight compounds, such as a charge-transporting compound, are added in many cases. In such cases, the film strength can be remarkably lowered due to a plasticizer effect of such low-molecular weight compounds, so that the occurrence of abrasion and scars at the surface layer on repetitive use becomes further serious problem. Further, a problem is liable to be encountered that such low-molecular weight compounds are precipitated or exuded during a storage of the electrophotographic photosensitive member.
For solving these problems, the use of a cured resin for constituting a charge transport layer has been proposed, e.g., in Japanese Laid-Open Patent Application (JP-A) 2-127652. According to this proposal, the resultant charge transport layer comprising a cured and crosslinked resin has provided remarkably increased durabilities against abrasion and scars during repetitive use. However, even in such a cured resin, a low-molecular weight compound-still functions as a plasticizer, and the above-mentioned precipitation or exudation thereof has not been basically solved.
Further, in a charge transport layer composed of an organic charge-transporting material and a binder resin, the charge-transporting performance is largely affected by the resin, and in case of using a cured resin having a sufficiently high hardness, the charge-transporting performance is liable to be lowered to result in an increased residual potential on repetitive use, so that it has not fully succeeded in satisfying both the hardness and electro-photographic performances.
JP-A 5-216249 and JP-A 7-72640 have disclosed an electrophotographic photosensitive member having a charge transport layer formed through reaction of a monomer having a carbon-to-carbon double bond and a charge-transporting material having a carbon-to-carbon double bond contained in the charge transport layer under application of heat or light energy. However, the charge-transporting material in the resultant charge transport layer is attached to the main chain of the binder polymer in the form of pendanrts, so that its plasticizer effect is not sufficiently excluded and the resultant charge transport layer does not exhibit a fully improved mechanical strength. Further, if the concentration of the charge-transporting material is increased, the crosslinkage density is lowered to fail in ensuring a sufficient mechanical strength.
As another solution, JP-A 8-248649 has disclosed an electrophotographic photosensitive member having a charge transport layer comprising a thermoplastic polymer having a main chain into which a group having a charge transporting function has been introduced. This is effective in preventing the precipitation of a low-molecular weight compound and improving the mechanical strength. As the binder is basically a thermoplastic resin, the mechanical strength thereof is limited, and the handling and productivity inclusive of the dissolving power for the resin cannot yet be said to be sufficient.
For the above reason, a research and. development work for providing a charge transport layer satisfying higher levels of mechanical strength and charge transporting performance in combination, is still being made.
A generic object of the present invention is to provide an electrophotographic photosensitive member having solved the above mentioned problems.
A more specific object of the present invention is to provide an electrophotographic photosensitive member having a surface layer exhibiting a high film strength leading to improved anti-abrasion and anti-scar characteristics, and also a good anti-precipitation characteristic.
Another object of the present invention is to provide an electrophotographic photosensitive member exhibiting very little change or deterioration of photosensitive member performances, such as increase in residual potential in repetitive use, thus being capable of exhibiting stable performances in repetitive use.
A further object of the present invention is to provide a process cartridge and an electrophotographic apparatus including such an electrophotographic photosensitive member.
A still further object of the present invention is to provide a process for producing such an electrophotographic photosensitive member.
According to the present invention, there is provided an electrophotographic photosensitive member, comprising: an electroconductive support and a photosensitive layer disposed on the electroconductive support; wherein the photosensitive layer comprises a polymerizate of a hole-transporting compound having at least two chain-polymerization function groups in its molecule represented by formula (1) below:
"Parenopenst"P1"Parenclosest"aA"Parenopenst"Zxe2x80x94(P2)d)b,
wherein A denotes a hole-transporting group, P1 and P2 independently denote a chain-polymerization function group and Z denotes a bonding organic group; a and b and d are independently an integer of at least 0 satisfying a+bxc3x97dxe2x89xa72 provided that if axe2x89xa72, plural groups P1 can be identical or different: if bxe2x89xa72, plural groups Z can be identical or different; and if bxc3x97dxe2x89xa72, plural groups P2 can be identical or different; and the hole-transporting group A is such that a combination of A with a number (a+b) of hydrogen atoms instead of "Parenopenst"P1"Parenclosest"a and "Parenopenst"Z"Parenopenst"(P2)d)b as in the formula (1) would provide a hole-transporting compound that is a compound represented by a formula selected from formulae (2), (3), (4) and (6), or a condensed cyclic hydrocarbon compound or condensed. heterocyclic compound having a group represented by formula (5) below: 
wherein R1, R2, R3 and R4 independently denote an alkyl group, aralkyl group or aryl group each capable of having a substituent; Ar1 and Ar2 independently denote an arylene group capable of having a substituent; and m is 0 or 1; 
wherein R5, R6, R9 and R10 independently denote an alkyl group, aralkyl group or aryl group each capable of having a substituent; R7 and R8 independently denote an alkylene group or arylene group each capable of having a substituent and Q denotes an organic group capable of having a substituent; 
wherein R11 and R12 independently denote an alkyl group, aralkyl group or aryl group each capable of having a substituent; and Ar3 denotes an aryl group capable of having a substituent with the proviso that the compound of the formula (4) includes at least one group represented by formula (5) below: 
wherein R13 and R14 independently denote an alkyl group, aralkyl group or aryl group each capable of having a substituent, or a hydrogen atom; Ar4 denotes an aryl group capable of having a substituent; and n1 denotes 0, 1 or 2; 
wherein Ar5 and Ar6 independently denote an aryl group capable of having a substituent; and R15 denotes an alkyl group, aralkyl group or aryl group each capable of having a substituent with the proviso that the compound of the formula (6) includes at least one group represented by formula (7) below: 
wherein R16 and R17 independently denote an alkyl group, aralkyl group or aryl group each capable of having a substituent, or a hydrogen atom; Ar7 denotes an aryl group capable of having a substituent; n2 is 0, 1 or 2.
According to the present invention, there is further provided a process cartridge, comprising: the above-mentioned electrophotographic photosensitive member and at least one means selected from the group consisting of charging means, developing means and cleaning means: said electrophotographic photosensitive member and said at least one means being integrally supported and detachably mountable to a main assembly of an electrophotographic apparatus.
The present invention further provides an electrophotographic apparatus, comprising: the above-mentioned electrophotographic photosensitive member, and charging means, developing means and transfer means respectively disposed opposite to the electrophotographic photosensitive member.
According to another aspect of the present invention, there is provided a process for producing an electrophotographic photosensitive member, comprising a photosensitive layer-forming step of forming a photosensitive layer on an electroconductive support; the photosensitive layer-forming step including a step of forming a coating layer comprising the above-mentioned hole-transporting compound of the formula (1) on the electroconductive support, and a step of polymerizing the hole-transporting compound in the coating layer.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawing.